The present disclosure relates to improved comparator offset correction devices.
When transistors included in comparators have fabrication variations, the threshold value of the comparators differs from a reference voltage due to the fabrication variations. For this reason, A/D conversion, or the like using comparators requires correction of the threshold value of the comparators in order to achieve highly accurate conversion.
Conventionally, in correcting the threshold value, the amount of offsets of comparators first has to be measured. In methods for measuring the offsets, as described in, for example, U.S. Pat. No. 6,822,501 and Japanese Patent Publication No. 2002-319863, the value of a reference voltage input to one input terminal of a comparator is fixed, an input voltage input to the other input terminal is increased from a voltage lower than the reference voltage to a high voltage to compute a difference between the input voltage and the reference voltage at a time of transition in an output from “0” to “1,” the input voltage is reduced from a voltage higher than the reference voltage to a low voltage to compute a difference between the input voltage and the reference voltage at a time of transition in the output from “1” to “0,” an average value of the obtained two differences is used an offset amount, and the inner potential, etc. of the comparator is changed based on the offset amount to correct the threshold value of the comparator.